Despite aggressive antimicrobial treatment regimens, over 100 million persons are infected annually worldwide with the sexually-transmitted obligate intracellular bacterial pathogen, Chlamydia trachomatis. During infection, C. trachomatis secretes effector proteins into the host cytosol that interfere with host signaling networks to dampen host immune defenses. Unfortunately infections are asymptomatic in the majority of men and women, development of long-term protective immunity against reinfection is inhibited, and therefore many infections become chronic and spur secondary pathologies like infectious blindness (trachoma), pelvic inflammatory disorder, ectopic pregnancy, and infertility. The serine protease chlamydial protease-like activity factor (CPAF) has emerged as a central chlamydial virulence factor due to its importance in lipid and membrane transport, actin cytoskeleton structure and dynamics, microtubule-based motors, lysosomal recognition of the inclusion, ERK/MEK signaling pathways, and the onset of programmed cell death and inflammation signaling. Using an inhibitor-based chemical biology approach, we recently developed two classes of CPAF inhibitors, and observed that inhibition of CPAF activity inhibited bacterial replication, destabilized the integrity of the parasitophorous inclusion vacuole housing replicating chlamydia, and resulted in bacterial cell death. We also determined that CPAF inhibition reprogrammed infected cells to re-initiate host immune defense responses to infection by secreting pro-inflammatory cytokines and activating an inflammasome-dependent programmed host cell death pathway. Based on these collective data, we hypothesize that CPAF inhibitors may form the basis for a new class of small molecule 'antimicrobial vaccines' that not only kill bacteria, but also may enhance adaptive and acquired immunity responses to chlamydial infections. Our goals for this proposal are to understand the role CPAF in C. trachomatis pathogenesis, to gain insight into the molecular level details of CPAF protease function, inhibition and identification of targets, and to determine the extent to which CPAF inhibitors can clear infections, rescue host immune defense activity, and protect against reinfection in a clinically relevant murine animal model of chlamydial genital tract infection.